Grinding machine



Aug. 10, 1943. L, STETLER GRINDING MACHINE Filed Nov. 6, 1940 5 Sheets-Sheet 1 INVENTOR Lowm 51mm ATTORNEYS L. STETLER GRINDING MACHINE 5 Sheets-Sheet 2 INVENTOR L0 WELL STETL'E'I? ATTORNEYS Aug. 10, 1943.

Filed Nov. 6, 1940 Aug. 10, 1943. STETLER GRINDING MACHINE Filed Nov. 6, 1940 5 Sheets-Sheet 3 1NVENTOR E in:

Aug. 10, 1943. Q STEITLER 2,326,264

GRINDING MACHINE Fiied Nov. 6, 1940 s Sheets-Sheet 4 INVENTOR LOWELL 5775715? ATTORNEYS mesneassignme'nts, V M land, Ohio 5 App ication Nove 1 Claims;

This inventionrelates o afmachine'forgrinding vertical surfaces and; particularly, to a'ma chine for regrinding slate blackboard's" which rotted. and Warped after years of have become use.

"Whenblacklj-oards havehe'en used andlwashed for several years in school rooms;v the surface offthe'blacklooards becomes "so ioughand rotted that they are "no longr' fit-f or juseg lnthe past, such blackboards hav usually beenfdiscarded d and new slate installed. Attempts to grindfoii the rotted surface of 'thefslate andthu restore the blackboards have not been especially successvful heretofore. I-Iand 'grindi ngis' slow and r e-- v quires the services of {a skilled operator, other: wise the Surface is left'in' a' rough and u'nservice-T ble condition; 7 Heretoifore no machine'jior accon nlishing the grindingoperation has beenJconi-f; 1

plet'ely satisfactory. Generally, 'suohiinachines',

following the design and I operationoj surface grinding machines employed iii-the metal working arts, floor finishing art, and the 1ike', have}been" designed to grind the surfaee being finishd to' plane surface. Such machines are unsatisfam tory for refinishing slate lolac kbcrardslaecause-J-the sheets of slate become. warped in time, and, if an attempt to grind the same to a plane isurfac e'is 7 made, certain portions of the slate aregr'ound so 7 thin that they break underthelpressure of grinde ing; or portions of the surfaceifiakefa'nd slough' on under the heat generated by taking too heavy a-cu't. Furthermoregsuoh machines; which must be rigid enough to grind the surface properly, I have been'too cumbersome and heavy .to be taken from room to room'in a school'orfroin school'to school. 7 y It' is an object of this inventiontosprovide a machine for 'regrinding blackboardsfwhich "are warned or u'rvecl so that an even de pth of. rotted slate will be ground ofi. all portions or theslate l leaving a smooth and evensurface; It is also an object of thisinvention to provide a, slate re-; grinding machine which will perrnit the pressure of the grinding head to be regulated asjth'e grind ing head moves over a warped 0-1 ourvedsurface. Itis another objector thisinvention toprovide a resiliently mounted grinding" headiwhich'may" be set for a given grinding pressure, Wh lCh'gTiDdF I ing pressure will remain substantially constant and not 'be disturbed "by small surface being reground. v-

' It is a still further objectof thisinvention e to provide 'a grinding machine'which' isiamply strongand rigid but which may be readily moved about from blackboard to blackboardin a school- Lowell seas; Cleveland, 01nd"a si horg j* mlier 6, 1944), Serial fie. 364535 variations in: the

to Samuel T. 'l iaas Qleve' mom; land-from robm to roon in" esch w; and 5 wnic msy be readily and simply disassern'hled fori transportationfroin school to sohool It is also an; obj eot of thief-invention to {provide a I grindin m c newmeh "will ijper nit the i use of isel eralfgrinding'fearriages in tandem ad permit th' length of the maohine to; lbe" iricr' 'ase'dor T de creased so that the Whole length of'a blackboard Y may be regroundil one set-up of the nac '10 A stillfurther object of thisinventio provide an' improved'drive ior aflgrindin carriage and to provide 'a 'carriageiqr ai riagesff V which will Permit the-grinding ihead. t grind to' the edge of ackboardiithe ed es looat'ed v acornera '5 f Other objects? and Y advantag es q i1 5 J-nVgn? tion will beiall i arent fro-1n the following sp' ifi cati n, claims; andjdrawings" i -which Fie "1 ,15 side 'e vetibn showing --a ;grii1ding n1fach thisfinventiori but with th w h eerme see r e nr ee l at rig: is, fragmentarvjild e ev t e I wring-4 is 'a jcross-lsetio pf 'ai' main ing 1 a era n, ozi ithsih -A ri i 2 v I Fig; 5;is a longitudinal section takenfalongthe ing he cy le oi'op a sh'own inFig. 6. I r g I In the drawings, ,in which likefref. ehcaoters refer to like parts,fl0 represents alvertgical end frame comprised'of apair of'verjticalrailsfl I; V

gene 12 spaced from "each other by-thejrl mgsglii on-the'end and suhported on the bottom bar It,v

placed on thetahle's-and a 'course acros'js blackboard is refinished 'firtr each courses completed, the tables n te lowere or elevated tocut-an adjacent colirseby 83 to provide a better truss'iconstruction; a V

To carry the assembled machine fromfloor to c 35 serving 1 as fulcrums; the elevatingsdrews" I 8 v a and 38 are adjusted so" that both the 'end frames 4 I and-3Q are substantiallyparallel to thefb1ack-' bo'ardto be refinished? Thefmachin'eis' then sevc ured'in position'settirigthehrakes 2D and? t i wri t-gamete" 54 ania snthewneis IM tit the;

1 the tam tob meansofitheir-frictiona1 -ngage;

" -ment- 'with the carriagetradkdfQ-Airriotor platform} is providedon under side with;

With the machine' thusfset 'up for-"Working; 3

grinding carriage'sjto be descrihedfibelbw,

ping-the motorfli'k s- It should he noted that-'th V a e to spana considerable distance metw entlc frames Wand 30. The legs' fi z andf 86,--

1 togetherby the clampslfl,cornbine tolform-a t ng and tQP'i-f 1 carriage Illfltowardthe end jframe l'fland pro -.v'ided' on one end with an}arcuate sIot IUS to ,7 1

'kingpost; "which, withlthe' guys; 11. I and 9Iff0rmthe tandem tables alight bilt com'paratively rigid truss constrilca" g tion for the tables 5 I1 and-80 c nnectedfintarldem. If the connected tables tend tof sa'g under the load of the griiidinfgcariiag'es; the legs 62 and 86 will be hel'dby the dowelsEQ so :thatthet'able. 7 frames E'Z and 92 wi l bearagains't each othei'f; and the legs 62 and 85 will tend to spread apart- 1 adjacent the casters 58'; -Su'c'hTsagging maybe" correctedby tightening up-the clamp l?! softhat Y the legs 62 and 86 will be drawn-'togethen*Pref erably; in order to insure that the guys H ai'id 9'! --are fully loaded,--' the clampll is tightened 'until 50 and 88 t'e'ndto bbW 11p? wardly slightly; f 7

From'ithe foregoing, it-is apparent tliat if 'a' l short blackboardeis' ftoT beground, th'mfachine mayTbe shortene'd 'by' simply disconneetin'g' the; gauxiliary table 80' Ifrom the power table Stand? the table frame 95,inserting thedo'wels' 69in the holes m the table rr ifne es-and engaging the pins 91 with the clamps 1! In suchian as under load may'fbe' corrected by adjusting-V-{the V tension on the'guy H by meanscflthe"nut 12'. Likewise,.the machine may belengthenedby con;

necting one or more additiohalauxiliary tables between the tablesifi'and 8B, Siich additional aiixiliary tables would fbe preferably provided with two crossed 'guyson; each 'sidein'st'eadbf the one diagonal guy'9I employedin the table:

M f: The grinding ihead'gear, to: -15 m 'h I 1 v a grindin'gjhead pinion; III Bamo'u'nted on' theffor the platform .I Il5 {is' a -verticaligrindingfhead as pivotably"mounted-thereon; V

slides in-the slot -lltllfatthe "otheren ofiithf, plate I 08, so that 1 the tra'ngular position or the I I3 for {the-grinding head shaft. b i'i orie' fe'ridpf the shaft andlwithin 'the bracketEI I lis mounted j a :large' {grinding head? gear 'I 4; f In the'l o'the'rif a, tend of the shaft andprotrl lding from theg'shroudf type; fpreierablii 'onef made according ito 'ibhe 'dis} closure ion my..'copending-application No; 35L333, vfiled Aug-11st 4-,:19i0; whichiwill permit} allimited line-.1lglfi connects theinterior-br ttle sh ud H2 i permit the dust ground fronr'ifthe blackboard. I I1 engaged by thei'grinding head o be V I whichisf mounted onithe plat'forin .I 65; The

driven axle-1'03translating thecarriage I00 .alon

pairof parallel grooved ways i I OE Whi'ch' engage the wayrcllers 1-61 f 'oun'ted ohth chassis 3| 0; so that tne: "platform; I 05 is slidably; mounted for longitudinal movement with 'respect to -t carriagelilfl and]transversegmovementwithrespect "to v the table- 5 9: On the iorward end-{of 3 s'embly'plate 10 8 offset-from thacentei'jof'the permit theigrinding head "assembly to to" d grinding head assemblin I I 0* comprises a U1-shaped bra cket l ll pivgteditoloneend -of thef 1 plate 108 and carrying a'suitablel'ock boltlwhich 7 be locked in the desired i adjustedfpositio V bracket" I'I'IM carries a flangedxeircular shroud II2 in the center of which ismounted a= bearing J12 is mo nted lag-l'suitable 'grinding theatr -I1 The 'grinding'lhead Ha -ma beg-of any desired angular movement-of the grinding-head respect .Sto the grindin'gihea'd shaftl t I suitable source of: vaciiuin: (n0tshown) to" the shroudand -removedito the ward end; of' th'e shaft 1, f9 Zdriven *by th motor 7 speed. reduction "afiorded by the grindin'gEhead-fi, '1

floor of a school, the end fr'ames I I] and :m'ay

' belifted entirely clear of the floor and yet main flats 22 and '42 sotha't the pinions TI and 94 engage the portionsof the racks ZI and 4| below the flats. xThe motor 13 is then stopped and the end frameswill-be held'in an elevated position above the floor. To transport the machine from school to school, the tables may-be readily dis I connected from each-other 'and "from" the end,

frames to permit the'machine tobe' compactly loaded on atruck or other vehiclejf LPOweT rida A power grinding carriage I00 runs'on the car'- 'riagetracks 54 and 55 of'the powertable 50;

The power carriage IE0 is comprised of a" chassis the carriage traversingfdriv from the'iriotorlflfl I63 carry groovedwheels I04 which engagethe 7 within suitable. limits,

s will enga'ge the blackboardl-l'l bya grinding" head pressure. regnlatingr 'ass'embly connecting" engaged betweenrthe'fcollar I25Qan'dthe block rcoupling lrfltto a speed reducer 128. A-fsmal gear I I4 and pinion- II 8 maybe jvaried by substituting,varioussizesi'of.pinions or gearsisinde the ipivotable mounting of the grinding head 'as I semblyv II I! on the forwa'rd plate I 08 willlperinit the distance :between the shaft? Q and "theis haft supporting thegrindingfihead gear to bevai-i The motor platformg-lfl5 and. e grinding jhead assembly I III are urgedpforwardly withizrespect to thecha's'sis lllligso'thatthe grindingfiheadf the platform I05 to the'chassis VIM. 'The'grind ing head pressure regulating assemblycomprises' j r anut I 2 I welded to the rear 'of-the platform T and ablo'ckulfig :A pressure regulating 'bolt -llt I. carrying'a: suitableghand-rwheel It2'4" 'i's"s1idablyreceived in'the block I22an d threadedly engagedslireloolt I23 hetween thegrnut, HI: and mock-1221 The platform (mils also urged forwardly;10y I The shaft H9 which extends". rearward-1i of? the, motor I2B-1is" connected "by V means'of a "suitable asprockett:aisimountedie igthe' qnibntsheit l39 th' isp'rocket chain EH! t drag emunt r-driveshait 'In operation, the operator setsiup;themachiner thel otal-pounds} pressurefon the blackboard:

. j =1" Withtthe iindings-hadengaging the black-' N not: causethe carriage to -vibrate because th'eentiren ma'ss "of the mechanism supported by the onLthe-mrface'wilrbe indicated by the distance betweenthe Ehand-wheel I24'and"the-bloek 1 22;

If thehand-wheel movement indicates the grind I ing pressure is approaching" the maximum or V minimum limits, the operator" mayimaintain'pres andpowe'rcarriage continue tofoperate.

Trjan 'm s b f r c i w i r e I Thel transfmissiori' forthe powerfcarriage lfl lf comprises a drive-shaft,lfigmounted parallelat'o the-oounterdrive-shaft I33 11 1 suitablev bearings d ve-shortlist:is;edema:spnoeketnwfi driv n? from th ma IV P QQ Qfi' 3?! onthe heit lt ihyla i o kfi h 2; m a st ft e-chain 3%;; .TI-hussasp ed reduci whieh ZIiVGSV hQ- sq fii mo e:

1 sprocket. I sz 1are di ose l with1.- pe. to l the.

-' "-wizith ofqth tableaso that thete th' rthe lergery' snr cket project sli ht y forwa yfizt e tee ofjthe srnall'eij1drivingzsprocket;129v when a the grinding-head (engages the blackboard I; l ;With t e utpiltsha t 1 30 otatinaih an mati n away r from lthet blackboardijl ljl the,-d riving tension on} f the:chain -?jl3 I;urgesthegplatformzlfifi anclthe r din h "a ainst the. blackboarda. 4 if I r mesh with sthefldriving pinion 4% by the} collars? IMtand-M; respectively. sliclablyqsplinedon 0 s-j.|4 1' e di list-end thus. cause the-pinion?! o drive th'e shaft 103 eitherzthrough t e pi ion Mlorthrolighthepiniomifl. I 2 {rhe cluteh 1451s; provifieel with' a shifting ee e. H6 nwhieha sh ftingo th f the short clutch arm' l 48 -of the bell-crank M9 is 1 engaged. "The belherank M8 "isipro'vzidedtwith a, 7 long throw-arm and-iszpivotally mounted cn.

the chassis Hiby'means of tha'pivot' lBIr-JIheL throwarm l5 0;ext endsbeyond theiframe Qfth.

sothatithepowertableiq is approximately paral; leltos-the sb'lackboard zwhich is. to be:-'reground: The] owerfoarriageglotfiis,thenfplacepton the -tas- 1 1318 150.; :theitable', J1 preferablvbe spaced fromthe'ablackbqard I I:1--so-that;;the grinding head H 5; v wil1=,=-be approximately inqe'ngagement; with: the. a *blaokboardsi'lfo set the pressure :of the grinding headgtpn the blackboard; theL hand:-whel I 24' is turnedrsto. incrasethe jspacebetween the collar s .{j-I2B; andthe; r'iut. I2 1; :thusgmovingl the platiori'n li05:;-forward1yiuntihthevgrindingfhead:engages then-blackboard; With 1 theplackboar d limiting l fthegforward movement of the -'plat'f0rm l UV5, ;sconfj-" tinned turnirig'j compresses 'tl'iespring 128 and; protects :the ,b iti I23 athr'oug'h; the bIoclr 1221i Thus thes-spaeeibetweentheharid-Whel lg l'and v the=bloekJ22?is'rinclioative of the pressure of the iilgrindingv-head-on tlieblackhoa'rjdiahd azscalex(not f" showmz--mayjbefconveniently" attached ito-vthe etriving pinionf shifted: by the; automat :carriesljby the' chassis. 1

' fianabteee i- Y transmission is: provided from-the shaft I I .9 or the motor: 120 through-ithe speedqreducerf I28 and;

'connte'rshaitl33 to thefdrive emi 5;, On th lsesured; a conical:

other end-of:

. fi h itfli Y 103 a anclare maintainegl in ax l t rj tweenihei iniens- H; and I 4.2 is a dou a e fl eielu' fc 5 s own; in a neutra position. mg. 6 but adapted; to engage wcorre,- spondingclutchfldogs cut-in the faces of the pinchassis'lfllftp permit theclutohxleijto be shifted manually, but the V throjzv-v arm ;I 5.0 :;-is normally-- wreversingflmeehanism.

1 The automatic reversing mechanism oomprises a shifting Earl freely slidable transversely of the: chassis lfll and having a lengthgreater than the-width ofthe chassissi- Mounted on the shift ing b a'r I 55 is a -lost motion- 1001132456: on which a pair. ofshiftingnutsjfil and [58 are spaced from eaeh'other andifixedll y means of suitable-jam v heart rotate ,fand' grind; and the "Carriage to 'trayers across? the poweri tabler-f The grind- 'ss re is especially steady' and; even bef f;th edesignand.constructioifofithe car 2 riage. .Sma-1L.projections' on the blackboard; will V spring-arm I62 mountedonthe throwarm I 58: r'

"The cycle of: operatioI1 oftthe, automatic ireversing mechanism for the carriage transmission is asifollows: Withthe clutch L45, in" a neutral positiomas shown in-Fig. 6; the mechanism :.is

set t throw-the ClufiChylijfltO engagement with, the forwardipinion lfl and thus cause-the care 7 riageito-be driven-=forwardly, that is, to the rightgas shown intheidrawingss The shifting, V

V hargl 55 has been pushediorwardly and is engaged by the'reverse 'stop pin 59' in the pin track 555 The leaf spri-ng ISO is flexedrearwarclly and urges the throw-arm l 50'forward1y's0 that the clutch I45 engages-the forward pinion- MI and the power carriage moves forwardly, Because the spring liifl'is preferably slightly over-fiexed to insure the engagement of theclutch I 45 withthe pinion I4 I,

as-the. carriage} moves 5forwardly; the spring I60 i V continues to press-the-shift-ing-bar l55-into enj j sure within" the "desired limits byf turning the r hanq-i wheeliand relieving or-incr'easing the' com pression of the spring whilethegrinding' heaci 'gagement with thereverse stop pin 59juntil'the carriage has moved forward a) distance 0, as ingiieategl i-ini Fig; .7; at which time the spring 516!) hasassumecl an .unflexed position. Y

I, The relative-positions of the several elements 7 of the carriage transmission and reversing mech- 'anism during normal forward travel of the carriage gis indicated{diagrammatically in Fig; 7 It shouldibe notedrthat the shifting bar is then pro jected forwardly of. the carriagejby an amount 7 indicatedz'by the dimension 1o The carriage continuesgztom'ove forwardly and when the forrvvard-stoppin 53 engagesthe forward end of the s I s Lrevrse. conical pinion; L ntil-4 mm r elyzrotata-q shifting. bar 155, the continued forwa'rdinubh .v

spring IBOtends to urgeatheshifting arm; 1:50

rearwardly, its force is insuflicient togathrowthe clutch I45 out of mesh with forward pinioniilii Thus,v the carriage 1B0 continues l to move. for-'1 wardly until 'therelatively rearwardimovement of the shifting bar 155 (actually the shiftingbar remainsstationary whilein engagement withifthe stop pin 58) forces the shifting arm "I56; into its neutral position by means of the-engagement of'the'shifting nut I51 with the block.I59.'-'}At this instant the parts are in'the relative position' showninFig'. 9, andthe leaf-spring lfio is: con

- siderably flexed in a rearward; directioni Due-to the moment arm extending-fromithe slot vHi'lgto plete's the shifting operation by urging the shifting arm I50 rearwardly and engaging-the clutch l45= with thereverse piniondlz; iThus the carf riage move's in a reverse-direction, i. e;,"- to theleft, as shown in the drawings, 'and'wh'enthe car regulating assembly foiflthe carriageggl 00:

The drive for the carriage Z50 'couldgofic 'Sin'c'e theidrive forithegcarriagerjlB5,. however; is I usually amply! powerfulli to: drive i not ionly itself 7 riage has moved 'a'distance indicated by theLdi-i 'mension o in Fig. ;10, the over-flexed Spring- Hill has straightened and the several-elements are in the relative position s'hownin Fig. 10 during the normal reverse travel of the carriage,-th shifting bar 155 being projected rearwardlyfas indicated by the dimension 1) in-Fig. l0.

- When the shifting bar I55 engages the reverse stop pin 59,;the spring ltil'is firstffleige'd iorwardly and the shiftingnut l58'engages the block I59, as shown in Figz'll; The carriagerlflilfcon the draw bar carriages; r

tinues to move rearwardly until the shifting-nut i has forced the arm-|50 andthe clutch I into the neutral position shown inrFigi 125 At this 1 instance the cycle'is"completed and the s'evlial elements are again in the relative positionshown V b From the fo regoingeln' it is apparent that th'e length of a course'ground-b'y the grinding head H5 may be fixed by setting the stop pin s or I detents 58 and 59 in the pin track 5'6 atlthed'e sired distance apart, and the-automatic revers ing'mecham'sm will reverse the carriage smoothly and positively. I Although theflcarriageltravels the arm I bythe shifting nuts: 1 51 andil58 the. main power carriages This inventiomthere fore, is not limited to "the"specificigembodiment .2 disclosed, GithBI'TinIWlTIQl or in' part," butirnayi'be,

I is limitedronlyby theappended'claims appreciably absorbs theshoclof the-reversing operation. It should also benoted thatafter the .7 traveler the carriage has been positively stopped and. the clutch disengaged by one of thestop pins;

the clutch is positively reengaged for drive the Auxiliary carriage? rWhen the machine is setup with the auxiliary table 80 for grinding-longblackboards, or theilike,

the work ispreferablyspeededxup by employing" an auxiliary'carriage 2B0. The auxiliary car-'- riage 2951s substantially similar-'to the power carriage'fllllfi, being comprised of a chassis Zillion which a'motor platform 205 is slidably mounted sembly 2 i U similar'to the grinding head assembly H0, except that itgis" offset to "the right ofthe t '60 opposite 'direction'bythe spring [60. o

T ,iorm' glia' is urged against tnepiakhpahi ,comprisedof anut ZZIJbIockTZfZZ,bolt-23;: 1 V 7 wheel 22%; collarg225; and qompression pring 225. The construction and;operation f" V and a'rod or -tube l2telesc'opically received there;- I l ;in.' A set 'screwqlis atithe opel e dofthe 'tube" -l H permitsr the length of the draw bar assembly 1 to" be set at one-half thelen'gth of the cou'rseto be groundg i .A suitable-removable securing'lme'ans 1 il l at the free end ofthe'tube Hi and ia similarf in tandem, as shown inl ig. 2, each grinding' head I H 1 will cut one-. halfi of the total-courseibeing ground. .It should beinoted that :the grindn'ig:"hea'd;assent-'1 V i i 35' jacent end frameQiThus, invtheevent thateither' j one or both of the iendfram'esmust beset against :1" va wal perpen'diculartto thesurface being; ground," I

0f the :mac'hine,likewisemorezthan one 'auxifiary ama'clfline oftheg'clas descr ed a'fi table 'with 'saicllfir'st end 'i'rame in veritically .ionon said elevatingf'shaft meshing'witlrjthefra k 0n saidi'first end" framehand tension memb table comprising a top-flush with and abuttlngm' '70,: pairvof end-flegsvadjacentsaid'powentable a sec-i 'ifran'le', tension members connecting said pai 'nall y of-said auxiliary tableiapinion ori 'sa i r e l 'iitoward the an ,f e. a

g n i ead as emb 2.! 0- t 2". moun d the plat r 0 m t r 1, 211 onthe a o m L th rin 'ih adc p s ez eeulatinaa H the f. g'rindingjheadtpressure. regulating assembly" orthercarriage 200 jis'fiidentical' with theconstrnc;-- tion and operationof the grinding head; press 'rei se, wbe;identical with theiidrivejiori thefcarriage 105.

but "aiwhole atrainbitcarriagesgthe carriageL201] is' preferably directly .conneoted-' 'o;,.the carriag r 15H byfajdrawbar assemblyaill he-era 'bar assemblyistpreferably'comprisedi of af tfubef i means; its at the'ire'e end o fthe rod- 1152 p rmits 'J assemblyLtQ: b'enconnected toithe' either prjbothfgrinding heads .Ecanjg'r'ind; to the 1 oorner of lthesurfacelibeing "groundiandlthjwall 5 against which the adjacent endgframelis setg, :It iszobviousthat; just; as more-thari-gtwoitables v maybe connected'ztogethertoincreaseitheglengthw carriage -jmaya be used on the :tablejin :addition to:

changediandwmodifiedlto meet s'peciiicfneeds as occasions filayfiaiiseri- This inventio he end-frame and a secon endf'ramig-iac of s end frames 'colnprisin rails; a rack; parall w said bottombar';' a poWe-r-tabie- 'corripr V a'first pair of 'end legs asecondp oi legs; secured to said 'top,frolleifs-v carried 'by-fs'aldfl first-pair'of legs demoiintably'enga'gingsaidpower r i slidable relationship a motor fca table, an elevatingshaftextending id of said table rotatable only by 's'aid -moto connectingfsaid pairs of end legsf; --*an'-auxi l the end of "said top sot said powerg-table, a} first 6nd 1 pair offend legs iadjacent' said'zseqond end;

end 'legs, an' elevating shaft 'e'iktendi gloiigitiidi l 1 said. first'clamping meansjc'onnect-ing said power table to said auxiliary table: in a, truss relation- 232 645 a a v fa: table structure comprising apw r:ane, meari demountably securing oneend-of.saidfpoweritable ship and adapted .to' connect said powertableto said table frame,

6.- In a machine of the class described in which an elevatable table carries ranielevating I shaft {extending to anend of [the table and a 7 ic p' isineea pa r of vertic l g de r ls -i a *hQ QntaL ot om,.m mb l 2 o n said su delra scom is n a banana-Lat t be t l s bpicallyece vedlonsa d barna ast r s pporting said baran d a caster,supp-orting said tube; one of said; casters being ;;.adjusta bly mounted to permitsaid' bottom member to be maintained in a horiz ontal positionswhen' d casters restronjanruneven fl' gn; Q 4

4 7. In a :machine of the class; described in t which end frames, @having vertical l guide rails demountably. support an elevatable-table struc ture, an elevatable table structure comprising ,a r

power table comprising a top, a; first pair of end 7 legs, and a second'pair of end legs, said legs be-Q ing integral with said top adjacent oppositeends thereof, means for demountably securing saidfirst pair'of end legs in a vertically =slidably re- Q; lationship with theguide rails of an end frame, g and-tension members extending from adjacent ,,;the top of said firstipair of end legs-to the secmountably connected tosaid' tablein aft/critically ,slidable relationship, a rackcarriedby said guide rails, meshing 5 withl thei 'pinion. on the elevating table to said table frame"; a pair of parallel car} and pair .ofend legs adjacent the bottom thereof; an elevating motor o'arried by :said; power 7 table, an elevating shaft driven by saidmotor and extending the length or said power table,

and a pinion on'the end of said elevating shaft adjacent an end frame; an auxiliary table-'comj prising a top, a first epair of end legs; a second I pair of end legsintegral with said; top adjacent opposite-ends thereof,-and tension r'nembers ex- 7 tending from adjacent the bottom: of said first pair of end legs to said" second pair of end legs adjacent the top ther eof; 'an' elevating'hshaft carried by said auxiliaryfltable; means coupling one'end of said shaft to the elevating shaft of said power table;,a pinion on the other end of ing means demountablygsecuring said first pair 7 of end legsof said auxiliary table-to thesecond 1 pairof end legs of said power tableto' form'a '7 of travel of said "power carriageon' said power] divided king post for a truss structureflcomprising the tops an'djtension members of said power and auxiliary tables, r r I g 8, In a machine of the class described in which end frames supp'ort'an elevatabletable structure,

a table structure comprising a power table, means demountably securing one end of. said 7 power,

o table to an end frame in a vertically slidable 'relationship, a table frame mounted in a'vertically slidable relationship on another endframe, .an 'e auxiliary table, means demountably' securing an;

end of said auxiliary'table to sa id table frame, and clamping meansrdemount'ably securing: said power table to said auxiliary table and adaptedito power table to; said demountably secure said table frame. -9. In amachine of the end frames suppo t' an elevatable' table structure;

class described in f and extending the length hereof inalignment with the carriage tracks of said L'poweritableQ a power carriagedrivenwheelsion said power ca *riage irictionally; engaging the carriage tracks 1 which a self-elevating table is-supported in a 1 structures, a table, a power 'carriage movable comprising a: chassis, a 'platform' ,carried'z by 'said prising ajgrinding head, afgr'inding head. shaft, a

necting said motor; to saidjgrinding" head shaft and adjustable resilient means connectingsaid a j platform and said chassis to p'erm'it'th'e pressure f i "of said grinding head on a surface being ground" said chassis andldriven by'fsai'd motdl .1 0 move said carriage along said table, and stop means for limiting the travel of said carriage' along said 1 to can end frameiin a vertically slidable relation; ship,v a' table frameimmmtedfin'a vertically -slidable relationship: on v anotherjendsir'ame; means for demountably securing said poWertab-le-tosaid 5 table-frame, a rotatablegelevating shaft :extend ingthe lengthofsaid powertalole means carried by theends, olfisaid elevating sh'aftland opera; tively connected; with said Send fr,am'es rto-nifa candlower said powerltable on said -.end frames; a a reversible elevating motor carriediby said power 3 table to, rotate .saidfilev'ating shaft, andgmeans V permitting said elevatingshaft'to rotate to lower; said power table;;o"nly ,w'hen said motor rotates saidshafixl .r'- T which 'endi'frames'rsupport an l elevatable j-table structure', ;a tablezstructure comprising aepower table, ;,means demountably' securingjrone end of said powerqtable man end;fram'e' a vertically slidable ,relation shipf atableframe mounted in a verticallylidable relationship on another jend frame, ,anau iIiary stable, means demountably i" securing an-end of; said auxiliary tablefito. said curing said power table :to Said 'auXili'ary'Qtable and adapted to demountablysecure sjaidpower;

riage tracks carried bysaid'power table and ex?- tending the length thereon-a; pair oi parallel carriage tracks carried bysaid "auxiliarytable saidpower tablefa motor carried'bysaid' power' j carriage, a transmission'c nnect nQSaid motor to K n said driven wheels; a reversingj mechanism ?ing cluded in said transmission; adjustably spaced- ,1 detent lcarried by said 'powerlcarriage to-actuate I g said reversing mechanism and. limit theflength,

table,fan auxiliary carriage movable on thecarriage track of said auxiliarytab1e, an adjustable a. draw-bar connecting said auxiliary carriage-to; V said power carriage, a 1 first "grinding head as!- sembly carried bysaid power carriage and connected to said motor, a second grinding head-assembly carried by said auxliliar'y. carriage, and an auxiliarygrinding head motor-connectedto said secondgrindinghead assembly. 11. In a machine a: of itheicl'assgdescribedin vertically movable relationship by endiirame along-the length of said: table, said-power table chassis and slidableonsaid chassis in ajdirecticn transverse to the length'of said table a grinding head assembly supported byjs'aid platformc'ombearing for said.;shaft,fand means securing said F bearing to said platform, a"grindi ng motorFca ried bysaid platform; speed 'redu'ction means contolrbe" regulated; transmission means carried by table.[ .7 H 12.vA machineas claimed in claim 11 nj whic meiiibf Qhsaiii platfdrm; a. bolt tnrga'nediy n J gageid' by said member, a hearing gn s'aid chassis,

"said {Bolt :being slidably rec'eivedztherein; 'a collar amaze;

-;"-13.-Ina machine of -the {class "described-a ""f'pdwer aarriage; a motp'rvarried by said cai'ria'ge, o;- Iii'OtOl shaft iirivri by'said motor, 1 and a grinding-heajd assembly fcomprisin'g; a" frame pivotably mountdjbn\saidplatfozm, a 'g rinding headfshaft carrie'd by said fr [mounted 'on' said grinfding Head shafa drivin'g means connecting said motor s'haft to said grind V ring head shaftj'said frame being pivdtable inia' ::.;p1an'e iberpen iculamoinsianeraefinea by he axes; 1015 said shafts t9 permitrthedistant pinidnorr saiii firive shaf a 'driveiizaxlaa first V piiiio'n' and 5a secoiid' pin'in on said drivan axle, shifting me'aiisto cause said drivelshflft to drive said axle in one directioh-thi'0ugii said "first {pinibn- 1 io drive said'axle in a reverse direction '.,throughasa.id second piniqnya nd detents' onsaid table to actuate said shifting; and meansperjmitting-the space be twen said d'ete'ntis t6 be varied to vary theidisi ane of travelibf'saidysar- I ria'ge 'albng-said-tabla'said shifting maan's coii1'- prising a. clutch adapteduto mesh -wi tsh ;saii i iirst axle pinion and 'said scond axie -piiiion,a'. be11 crank actuating 's'aid l cl itch, a iast mfotion member actuating said bell wank; and adapted to be' disengaged 5? clutch; in j other pf said axie pin adrive:- shafi engaged and actuated by said fietents; and a springgconneo'ting said 10st meibio i nie'mberf and said bell ci afikwhei by th es engagement {of ons of said detents by said last motion membemnhile "cai'd carriage is ih ihgtihfiiges said-spring E'and positivlyflisngagessaid "clutch from one of said axie' pinioiis"a ddshefflexed spring. throws-said engagement -'with-"-the vrse'the" travel of said arpiage;

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